It is well known that there is energy in the motion of water created by wind moving over the surface. The surface profiles are referred to as waves and various float-type devices have been designed to tap the energy at the air/water interface The energy available in this region is only a portion of the total energy available, as the water particles are in motion to a considerable depth which will become evident in a later section hereof.
Wind moving over water transfers its energy to the water by setting the water in motion. This movement of the water is an essentially harmonic motion down to the ocean bottom. In deep ocean, the distance of water particle travel at a depth equal to one-half the wave length (wave length [L] is the distance from one crest to the next) is four percent of the distance of particle travel at the surface. Because energy is related to the square of the motion of water particles, over 99.8 percent of the total energy is within a depth of one-half the wave length from the surface. The amount of the wind's energy stored in the moving water beneath the waves depends primarily on the wind velocity and the length of time and the distance over which the wind has been blowing, since the wave height and wave length are determined by these conditions.
Float-type devices interacting at the water surface are relatively inefficient because they do not utilize the large amount of energy stored in the moving water beneath the wave profile. The total amount of energy stored in the water is of two forms, kinetic and potential. The principal object of this invention is to provide a device which will extract both forms of energy with high efficiency by interacting with the water beneath the waves to the depth necessary.
In accordance with a specific embodiment of the invention which is described in detail hereinafter, a member is supported in the water in a manner such that it will be moved back and forth in an oscillatory manner by the movement of the water beneath the waves. This member is sometimes referred to hereinafter as a "sail" and preferably, although not necessarily, is constructed so as to change its profile with each reversal of the direction of water movement. The mathematical descriptions of water motion below the surface of waves may be found in "Theoretical Hydrodynamics" by Milne-Thompson (Library of Congress 60-13815, pages 388-404), and "Estuary and Coastline Hydrodynamics" published by McGraw Hill (Library of Congress 65-27677, pages 24-54). Selected equations from these texts necessary to explain the movement of water beneath waves are presented in later sections hereof.
Numerous devices of the type contemplated by this invention may be grouped together in "farms" in the ocean or any large body of water to generate sufficient electrical energy to serve the needs of entire communities. Bearing in mind that the natural motion of the water is the source from which this energy output is derived, the system is non polluting and does not deplete any of our natural resources.